Photon Science Roadmap- for Research Infrastructures 2025-2028 by the Swiss Photon Community
Majed Chergui - elected to the European Academy of Sciences
Ruth Signorell - elected to the European Academy of Sciences
Proof of concept ERC Grant for Ursula Keller Dual-comb laser driven terahertz spectrometer for industrial sensing (DC-THz)
Farewell and Welcome!Chris Milne leaves for the European XFEL, Camila Bacellar takes over
SY-GAIA expedition - measures aerosols in the North-Atlantic
Synergy grants for MUST-AssociatesSylvie Roke (EPFL) and Gebhard Schertler (PSI/ETH).
Promotion to Associate Professor of Photonicscongratulations to Rachel Grange!
First light in the SwissFEL Maloja endstation- on track for first experiments in 2021
New scientific highlights- by MUST PIs Chergui, Milne, Wörner, Vaníček and Röthlisberger

Ultrafast Transient Increase of Oxygen Octahedral Rotations in a Perovskite

August 9, 2019  (more to follow)

Via femtosecond hard x-ray diffraction we identified a perovskite system that complements the rare selection of materials in which a symmetry broken phase can be transiently stabilized by photoexcitation. EuTiO3 exhibits a second order purely structural phase transition (TC = 290 K) which is characterized by an antiferrodistortive rotation of the oxygen octahedra (see figure, left unit cell) with the rotation angle being the order parameter. We directly monitor this angle upon photoexcitation across the band gap (data points) via x-ray pulses obtained from a FEL. Within the first few-hundred femtoseconds after excitation we observe a transient increase of rotation angle. This stands in contrast to the situation of an increased temperature for which the order parameter decreases. We ascribe the surprising increase of the order parameter to a transient effective change of ionic sizes that transforms directly into an ultrafast change of the Goldschmidt tolerance factor. The ability to modify the Goldschmidt tolerance factor provides another tuning parameter to control electronic and magnetic properties of perovskites on ultrafast timescales.

Reference: M. Porer, M. Fechner, M. Kubli, M.J. Neugebauer, S. Parchenko, V. Espositio, A. Narayan, N. A. Spaldin, R. Huber, M. Radovic, E. M. Bothschafter, J. M. Glownia, T. Sato, S. Song, S. L. Johnson, and U. Staub.
Phys. Rev. Research 1. 012005 (R) (2019). DOI: 10.1103/PhysRevResearch.1.01005
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